Changelog - Travis: run the tests on PHP 8/nightly

Author: grogy

CHANGELOG.md

@@ -9,6 +9,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 ### Internal
 
 - PHPUnit - Make the unit tests cross version compatible [#12](https://github.com/php-parallel-lint/PHP-Var-Dump-Check/pull/12) from [@jrfnl](https://github.com/jrfnl).
+- Travis: run the tests on PHP 8/nightly [#13](https://github.com/php-parallel-lint/PHP-Var-Dump-Check/pull/13) from [@jrfnl](https://github.com/jrfnl).
 
 ## [v0.5] - 2020-08-17